Multiyear Temporal Changes in Chlorinated Solvent Concentrations at 23 Monitored Natural Attenuation Sites

Newell, Charles J.; Cowie, Iain; McGuire, Travis M.; McNab, W. W.

doi:10.1061/(asce)0733-9372(2006)132:6(653)

Cited by 45 publications

(51 citation statements)

References 11 publications

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“…In contrast, analytical solutions can be highly efficient, but are generally limited to simpler domains with homogeneous and isotropic properties. This behavior has been observed in both field (e.g., McGuire et al 2006;Newell et al 2006) and numerical modeling studies (e.g., Parker and Park 2004). Although the source concentration response to source mass reduction can be highly variable (e.g., Parker and Park 2004), Falta et al (2005) describes a special case where source concentration is linearly proportional to source mass, and both source mass and source concentration simultaneously exhibit exponential decay with time.…”

Section: Introductionmentioning

confidence: 76%

“…An example of the latter is the study by Falta et al (2005) who developed an analytical source function for NAPL source dissolution and remediation. In a review of DNAPL sites undergoing natural attenuation, Newell et al (2006) reported downgradient source concentration half-life values from as low as 0.7 years for tetrachloroethylene (PCE) to constant (or even increasing) concentrations for trichloroethylene (TCE). This behavior has been observed in both field (e.g., McGuire et al 2006;Newell et al 2006) and numerical modeling studies (e.g., Parker and Park 2004).…”

Section: Introductionmentioning

confidence: 99%

“…Based on the findings of McGuire et al (2006) and Newell et al (2006) for sites impacted by chlorinated solvents, source zone treatment is represented mathematically by three different generic concentration vs. time functions: (1) a "Type A" constant concentration source that does not experience a change in concentration with time; (2) a "Type B" source that utilizes a constant concentration until time t * following which concentrations are immediately reduced to zero (complete source elimination); and (3) a "Type C" source that utilizes a constant concentration until time t * following which concentrations decay exponentially. Based on the findings of McGuire et al (2006) and Newell et al (2006) for sites impacted by chlorinated solvents, source zone treatment is represented mathematically by three different generic concentration vs. time functions: (1) a "Type A" constant concentration source that does not experience a change in concentration with time; (2) a "Type B" source that utilizes a constant concentration until time t * following which concentrations are immediately reduced to zero (complete source elimination); and (3) a "Type C" source that utilizes a constant concentration until time t * following which concentrations decay exponentially.…”

Section: Introductionmentioning

confidence: 99%

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Plume Detachment and Recession Times in Fractured Rock

West

Kueper

2010

Groundwater

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The influence of source zone concentration reduction on solute plume detachment and recession times in fractured rock was investigated using new semianalytical solutions to transient solute transport in the presence of advection, dispersion, sorption, matrix diffusion, and first-order decay. Novel aspects of these solutions are: (1) the source zone concentration behavior is simulated using a constant concentration with the option for either an instantaneous reduction to zero concentration or an exponentially decaying source zone concentration initiated at some time (t*) after the source is introduced, and (2) different biodegradation rates in the fracture and rock matrix. These solutions were applied for sandstone bedrock and revealed that biodegradation in the matrix, not the fracture, may be the most significant attenuation mechanism and therefore may dictate remediation time scales. Also, instantaneous and complete source concentration reduction in aged plumes may not be beneficial with respect to plume response because back-diffusion can sustain plume migration for long periods of time. Moderate source zone concentration reduction has a similar impact on the rate of advance of the leading edge of the plume as aggressive concentration reduction. If the source zone concentration reduction half-life is less than the plume decay half-life, then volatile organic compound (VOC) mass sequestered in the rock matrix will ultimately dictate plume persistence and not the presence of the source zone.

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Section: Introductionmentioning

confidence: 76%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Plume Detachment and Recession Times in Fractured Rock

West

Kueper

2010

Groundwater

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“…Evaluation of long-term monitoring records from individual monitoring wells indicates that linear and first-order models provide similar quality fits to the data (Newell et al 2006;McHugh et al 2011). For the purpose of estimating the long-term attenuation rate, the statistical methods for the two models are almost identical.…”

Section: Use Of Regression Analysis To Estimate Attenuation Ratesmentioning

confidence: 93%

Time vs. Money: A Quantitative Evaluation of Monitoring Frequency vs. Monitoring Duration

2016

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The National Research Council has estimated that over 126,000 contaminated groundwater sites are unlikely to achieve low ug/L clean-up goals in the foreseeable future. At these sites, cost-effective, long-term monitoring schemes are needed in order to understand the long-term changes in contaminant concentrations. Current monitoring optimization schemes rely on site-specific evaluations to optimize groundwater monitoring frequency. However, when using linear regression to estimate the long-term zero-order or first-order contaminant attenuation rate, the effect of monitoring frequency and monitoring duration on the accuracy and confidence for the estimated attenuation rate is not site-specific. For a fixed number of monitoring events, doubling the time between monitoring events (e.g., changing from quarterly monitoring to semi-annual monitoring) will double the accuracy of estimated attenuation rate. For a fixed monitoring frequency (e.g., semi-annual monitoring), increasing the number of monitoring events by 60% will double the accuracy of the estimated attenuation rate. Combining these two factors, doubling the time between monitoring events (e.g., quarterly monitoring to semi-annual monitoring) while decreasing the total number of monitoring events by 38% will result in no change in the accuracy of the estimated attenuation rate. However, the time required to collect this dataset will increase by 25%. Understanding that the trade-off between monitoring frequency and monitoring duration is not site-specific should simplify the process of optimizing groundwater monitoring frequency at contaminated groundwater sites.

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“…For example, Newell et al 84 present data from 23 chlorinated solvent MNA sites monitored for 5-15 years. The survey showed a median reduction in contaminant concentration of 74%.…”

Section: Chlorinated Solvent Plumesmentioning

confidence: 97%

Monitored natural attenuation of organic contaminants in groundwater: principles and application

Rivett¹,

Thornton²

2008

Proceedings of the Institution of Civil Engineers - Water Manag

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This paper reviews the conceptual and technical basis underpinning the use of monitored natural attenuation (MNA) for the management of organic contaminants in groundwater. MNA has important advantages over engineered remediation technologies for groundwater. Its significance will increase across the international community generally and its application for the management of petroleum hydrocarbons and other aromatic compounds will expand. Its application to other contaminants such as chlorinated solvents requires further qualification, although it has demonstrable potential for these. Long-term dissolution of non-aqueous-phase liquid (NAPL) sources is a major issue affecting remediation time-frames for MNA. Source zone remediation in conjunction with MNA will be required for many contaminated sites to meet typical regulatory time-frames permitted for MNA application. Internationally, there is general consensus in the scientific basis and assessment methods included in the technical guidance or protocols supporting the application of MNA. It is not a ’do-nothing’ remediation strategy, but requires site-specific characterisation, scientifically based analysis and a long-term commitment to monitoring, data collection and rigorous technical evaluation for ongoing performance assessment. Additional remediation technologies may be required to support MNA during the remediation programme and the decision to implement MNA should consider the large body of MNA literature that now exists and is summarised here.

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Multiyear Temporal Changes in Chlorinated Solvent Concentrations at 23 Monitored Natural Attenuation Sites

Cited by 45 publications

References 11 publications

Plume Detachment and Recession Times in Fractured Rock

Plume Detachment and Recession Times in Fractured Rock

Time vs. Money: A Quantitative Evaluation of Monitoring Frequency vs. Monitoring Duration

Monitored natural attenuation of organic contaminants in groundwater: principles and application

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